HETEROMORPHOSIS 173 



li) It was possible to cause the growth of roots in the 

 middle of a stein by bringing this point in contact with 

 solid bodies. 



5 a) It was possible to grow tips from the basal cut end of 

 a stern of Sertularia polyzonia by fixing the stems in the 

 aquarium with their basal ends upward (toward the source 

 of light). New roots were usually formed at this end in 

 addition to the new tips (Fig. 22, a, b). 



6) So far as my present experiments go, new branches 

 were formed only on that side of the old stem or root which 

 was turned toward the light. 



6. It was possible to produce biapical animals in Gono- 

 thyrae Lovenii. 



II. In a long series of animals, particularly Actinians, I 

 have not yet succeeded in causing a heteromorphosis of any 

 kind. In these animals the position of the regenerated 

 organ is determined (as far as our present knowledge goes) 

 by the orientation of the fragment occupied in the uninjured 

 organism, a new head is formed at the oral edge of a piece 

 of such an animal, while a new foot is regenerated at the 

 aboral end. This law governs regeneration, not only in 

 Actinia, but also in Hydra, in certain starfish which I have 

 studied, in a series of worms, snails, crustaceans, and animals 

 still higher in the scale, 



III. The same behavior in organization is therefore found 

 in the animal kingdom as in the vegetable. As is well 

 known, it is possible to control the position of a new organ 

 (just as in the animals given under heading I) in certain 

 plants, while in others (as in Actinians) regeneration is 

 dependent upon conditions which are at present unknown, 

 and are apparently internal 



IV. The following are mentioned as some of tin- diUVivMi 

 forms of irritability which influence the orientation of animal 

 organs : 



